Negative screening for 12 rare LRRK2 pathogenic variants in a cohort of Nigerians with Parkinson's disease

An overview of the worldwide distribution of LRRK2 mutations in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder with significant genetic influence. The LRRK2 gene is a major genetic contributor, particularly the Gly2019Ser mutation. This focused review investigates the global distribution of LRRK2 mutations, with emphasis on Gly2019Ser and other pathogenic variants. Prevalence rates of Gly2019Ser are highest in North Africa and the Ashkenazi-Jewish population, indicating a potential common ancestor and founder effect. Other LRRK2 mutations, including Asn1437His, Arg1441Gly/Cys/His, Tyr1699Cys and Ile2020Thr, exhibit varying global prevalences. Understanding these distributions enhances our knowledge of PD genetics and aids personalized medicine. Further research is crucial to unravel clinical implications and develop targeted therapies for LRRK2 mutation carriers.

The Landscape of Monogenic Parkinson's Disease in Populations of Non-European Ancestry: A Narrative Review

INTRODUCTION

There has been a bias in the existing literature on Parkinson's disease (PD) genetics as most studies involved patients of European ancestry, mostly in Europe and North America. Our target was to review published research data on the genetic profile of PD patients of non-European or mixed ancestry.

METHODS

We reviewed articles published during the 2000-2023 period, focusing on the genetic status of PD patients of non-European origin (Indian, East and Central Asian, Latin American, sub-Saharan African and Pacific islands).

RESULTS

There were substantial differences regarding monogenic PD forms between patients of European and non-European ancestry. The G2019S Leucine Rich Repeat Kinase 2 (LRRK2) mutation was rather scarce in non-European populations. In contrast, East Asian patients carried different mutations like p.I2020T, which is common in Japan. Parkin (PRKN) variants had a global distribution, being common in early-onset PD in Indians, in East Asians, and in early-onset Mexicans. Furthermore, they were occasionally present in Black African PD patients. PTEN-induced kinase 1 (PINK1) and PD protein 7 (DJ-1) variants were described in Indian, East Asian and Pacific Islands populations. Glucocerebrosidase gene variants (GBA1), which represent an important predisposing factor for PD, were found in East and Southeast Asian and Indian populations. Different GBA1 variants have been reported in Black African populations and Latin Americans.

CONCLUSIONS

Existing data reveal a pronounced heterogeneity in the genetic background of PD. A number of common variants in populations of European ancestry appeared to be absent or scarce in patients of diverse ethnic backgrounds. Large-scale studies that include genetic screening in African, Asian or Latin American populations are underway. The outcomes of such efforts will facilitate further clinical studies and will possibly contribute to the identification of either new pathogenic mutations in already described genes or novel PD-related genes.

Transforming Parkinson's Care in Africa (TraPCAf): protocol for a multimethodology National Institute for Health and Care Research Global Health Research Group project

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disorder and, according to the Global Burden of Disease estimates in 2015, was the fastest growing neurological disorder globally with respect to associated prevalence, disability, and deaths. Information regarding the awareness, diagnosis, phenotypic characteristics, epidemiology, prevalence, risk factors, treatment, economic impact and lived experiences of people with PD from the African perspective is relatively sparse in contrast to the developed world, and much remains to be learned from, and about, the continent.

METHODS

Transforming Parkinson's Care in Africa (TraPCAf) is a multi-faceted, mixed-methods, multi-national research grant. The study design includes multiple sub-studies, combining observational (qualitative and quantitative) approaches for the epidemiological, clinical, risk factor and lived experience components, as appropriate, and interventional methods (clinical trial component). The aim of TraPCAf is to describe and gain a better understanding of the current situation of PD in Africa. The countries included in this National Institute for Health and Care Research (NIHR) Global Health Research Group (Egypt, Ethiopia, Ghana, Kenya, Nigeria, South Africa and Tanzania) represent diverse African geographies and genetic profiles, with differing resources, healthcare systems, health and social protection schemes, and policies. The research team is composed of experts in the field with vast experience in PD, jointly led by a UK-based and Africa-based investigator.

DISCUSSION

Despite the increasing prevalence of PD globally, robust data on the disease from Africa are lacking. Existing data point towards the poor awareness of PD and other neurological disorders on the continent and subsequent challenges with stigma, and limited access to affordable services and medication. This multi-site study will be the first of its kind in Africa. The data collected across the proposed sub-studies will provide novel and conclusive insights into the situation of PD. The selected country sites will allow for useful comparisons and make results relevant to other low- and middle-income countries. This grant is timely, as global recognition of PD and the public health challenge it poses builds. The work will contribute to broader initiatives, including the World Health Organization's Intersectoral global action plan on epilepsy and other neurological disorders.

TRIAL REGISTRATION

https://doi.org/10.1186/ISRCTN77014546 .

Review of the epidemiology and variability of LRRK2 non-p.Gly2019Ser pathogenic mutations in Parkinson’s disease

Parkinson’s disease (PD) is a heterogenous neurodegenerative disorder. Genetic factors play a significant role, especially in early onset and familial cases. Mutations are usually found in the LRRK2 gene, but their importance varies. Some mutations, such as p.Arg1441Cys or other alterations in the 1441 codon, show clear correlation with PD, whereas others are risk factors found also in healthy populations or have neglectable consequences. They also exhibit various prevalence among different populations. The aim of this paper is to sum up the current knowledge regarding the epidemiology and pathogenicity of LRRK2 mutations, other than the well-established p.Gly2019Ser. We performed a review of the literature using PubMed database. 103 publications met our inclusion criteria. p.Arg1441Cys, p.Arg1441Gly, p.Arg1441His, p.Arg1441Ser are the most common pathogenic mutations in European populations, especially Hispanic. p.Asn1437His is pathogenic and occurs mostly in the Scandinavians. p.Asn1437Ser and p.Asn1437Asp have been reported in German and Chinese cohorts respectively. p.Ile2020Thr is a rare pathogenic mutation described only in a Japanese cohort. p.Met1869Thr has only been reported in Caucasians. p.Tyr1699Cys, p.Ile1122Val have only been found in one family each. p.Glu1874Ter has been described in just one patient. We found no references concerning mutation p.Gln416Ter. We also report the first case of a Polish PD family whose members carried p.Asn1437His.

The Current State of Parkinsonism in West Africa: A Systematic Review

Parkinsonism is one of the most common neurodegenerative diseases among the elderly. Africa is experiencing an increasing burden of age-related conditions including parkinsonism. However, there is not enough data on the prevalence, symptoms, and management of the disorder in West African patients. This systematic review examines the current state of parkinsonism in West Africa by discussing its epidemiology, symptomatology, and treatment. We searched PubMed, BioMed Central, and AJOL databases from January 2000 to December 2020 for studies on parkinsonism conducted in West African countries. We included 32 studies in this review: 23 from Nigeria, 5 from Ghana, and 1 each from Benin, Mali, Niger, and Senegal. Out of the 32 reviewed studies, 11 focused on the prevalence of parkinsonism, 4 examined the genetics of Parkinson's disease (PD), and 17 described the symptomatology and therapy of parkinsonism. The prevalence of parkinsonism in West Africa ranges from 6.0% to 8.3% of neurologic admissions/consultations. The estimated crude prevalence of PD in West Africa varies from 15 to 572 per 100,000 people. Thus far, no pathogenic genetic variants have been associated with PD in the region. Levodopa is frequently used singly or in combination with other medications to manage parkinsonian symptoms, which is consistent with reports from other African regions. Most of the reviewed studies focused only on PD, limiting assessment of other forms of parkinsonism. Almost all the prevalence studies were hospital-based and monocentric, making it impossible to accurately estimate the true prevalence of parkinsonism in West Africa. Larger community-based prevalence studies are recommended to enable accurate quantification of disease burden. Future genetic investigations should consider a wider array of gene mutations associated with parkinsonism. Moreover, public health surveillance strategies should be established to monitor the epidemiology of the disorder.